Question

In the processing of hnRNA in eukaryotic cell, the primary transcripts are processed in the following sequence.

• A. Splicing, Capping, Tailing
• B. Tailing, Capping, Splicing
• C. Splicing, Tailing, Capping
• D. Tailing, Splicing, Capping

Hint:

Memory trick: SCT $\rightarrow$ Splicing, Capping, Tailing

Answer 1

The Correct Option is A

Concept: In eukaryotes, heterogeneous nuclear RNA (hnRNA) undergoes processing to become mature mRNA.
• Splicing: Removal of introns and joining of exons
• Capping: Addition of methyl guanosine cap at 5' end
• Tailing: Addition of poly-A tail at 3' end

Step 1: Understand sequence of processing.
First, non-coding regions (introns) are removed.

Step 2: Stabilization steps.
Then, capping and tailing occur to stabilize mRNA and aid in translation.

Step 3: Correct order.
Splicing $\rightarrow$ Capping $\rightarrow$ Tailing

Step 4: Analyze options.
• (A) Correct sequence
• Others incorrect

Step 5: Conclusion.
Thus, the correct order is splicing, capping, and tailing. Final Answer: Option (A)